Inkjet recording apparatuses have been extensively known and used in various fields. The inkjet recording apparatus has a recording head formed with a plurality of nozzles. Ink droplets are selectively ejected from the nozzles onto a recording paper to record images thereon. In use, an ink cartridge is mounted on the inkjet recording apparatus to supply ink to the recording head.
The ink cartridge has an ink chamber for storing ink therein. An air-hole is formed in the ink chamber to be fluidly communicable between the ink chamber and atmosphere. Air is introduced into the ink chamber from the air-hole to replace an amount ink consumed with a corresponding amount of air. Introduction of air into the ink chamber is essential to smoothly perform ink ejection.
In order to prevent ink from being leaked from the ink chamber through the air-hole, a porous or foam membrane is affixed to the air-hole. The membrane allows air to pass therethrough but interrupts ink from passing therethrough. In some inkjet recording apparatuses, a sub-tank is mounted in a carriage together with the recording head, and an air-hole and a membrane are provided in the sub-tank rather than the ink cartridge.
There has been known an ink cartridge having a slanted air communication channel connecting the ink chamber and the air-hole. If this type of ink cartridge or an inkjet recording apparatus in which such an ink cartridge is mounted is eventually inclined, ink stored in the ink chamber may move toward the air-hole and ink may be brought into contact the membrane sealing the air-hole. If it is the case, air is difficult to pass through the membrane, so that shortage of air introduction into the ink cartridge or into the sub-tank will occur and hence smooth ink ejection cannot be achieved or ink ejection failure may occur. The problem of ink ejection failure may not be resolved even if the ink cartridge or the sub-tank is returned to the normal posture from the inclined state if ink does not return to the ink chamber from the air-hole but remains in the clinging state to the membrane. More specifically, when the ink cartridge or the inkjet recording apparatus is inclined from the normal state, ink moving toward the air-hole expels air out of the ink cartridge through the membrane. When the ink cartridge or the inkjet recording apparatus is returned to the normal posture from the inclined state, a relevant amount of air needs to be smoothly introduced into the ink chamber attendant to the movement of the ink toward the ink chamber. However, this cannot be achieved if ink still clings to the membrane. Air does not pass through the ink-clinging portion of the membrane, so that ink does not move or is difficult to move toward the ink chamber. In consequence, ink remains in contact with the membrane, thereby making it difficult to recover the air permeability of the membrane.